Fabric treating compositions have been developed which are capable of imparting one or more of a variety of properties to articles of clothing, such as softness, fragrance, brightening, bodying, reduced static, anti-soiling, anti-creasing and others. Two of the most prominent commercially available methods of treating clothing include liquid fabric softeners employed in washing machines, and “dry” dryer sheets used in clothes dryers.
One liquid fabric softener is commercially available from The Proctor & Gamble Company of Cincinnati, Ohio under the trademark Downy®. Liquid fabric softeners of this general type are comprised of cationic compounds, and particularly quaternary ammonium and imidazolinium salts, in the form of liquid emulsions. They are introduced into the washing machine and added to the clothing during the rinse cycle.
Although effective in imparting softness and reducing static cling, liquid fabric softeners have a number of deficiencies. One limitation is that they are inconvenient to use. Often sold in relatively large and heavy containers, liquid fabric softeners must be poured into the relatively small cap of the container, a cup or other measuring device to obtain the proper quantity for a particular size load of wash. The liquid softener is then poured into a receptacle in the washing machine where it is held until the rinse cycle begins. It is easy to spill the liquid softener, both when measuring and pouring it into the washing machine, and then one needs to clean the cap or other measuring device after use.
Another problem with liquid fabric softeners is that the entire content of the washing machine is subjected to the softening agent when it is applied in this fashion. It may be desirable to soften only some of the clothes being washed in a particular washing cycle, but in order to do that the clothing must be separated beforehand and additional loads of wash run. This is not only inefficient but uses additional energy and water.
A still further deficiency of liquid fabric softeners is their effect on the flammability of clothing items. According to tests conducted by Consumer Reports, liquid fabric softener added to the rinse water in washing machines accelerates the burn rate of most fabrics tested. For example, in one test, a terry-cloth bathrobe laundered with liquid fabric softener took just 1.9 seconds to burn a five inch path whereas the same fabric without the fabric softener took 13 seconds to burn the same five inch path. Although the rate of burn varies with the type of fabric, seconds count when clothing catches fire.
With respect to “dry dryer sheets,” one product of this type is commercially available from The Proctor & Gamble Company of Cincinnati, Ohio under the trademark Bounce®. Dryer sheets of this type generally comprise sheets of non-woven material impregnated with a composition usually consisting of a cationic softening agent, antistatic agents, dispersing agents and a fragrance. The softening or other fabric treating agent is applied to the non-woven material and then dried in an oven so that it is completely “dry” when ready for use. One or more dry dryer sheets are placed into a rotary clothes dryer with freshly laundered, damp items of clothing, where they remain for the entire drying cycle. The composition on the sheet of non-woven material is released in the course of the drying cycle as a result of the heat within the clothes dryer, and contact with the clothing induced by the tumbling action of the dryer.
Although much more convenient to use than liquid fabric softeners, the dry dryer sheets described above also have a number of limitations. First, dry dryer sheets exhibit relatively poor softening capability compared to liquid fabric softeners. One reason for this is that dry dryer sheets depend to a large extent on physical contact with the clothing within the dryer during the drying cycle in order to effectively transfer the softening composition to the clothes. If the dryer sheet becomes trapped within the sleeve of a shirt, a pant leg or the like, it cannot make contact with other articles of clothing within the dryer. Even if the dry dryer sheet freely contacts the clothing during a drying cycle, the softening agent it carries does not penetrate the fabric to the same extent as liquid fabric softener in the rinse cycle of the washing machine.
Another limitation of dry dryer sheets is that a relatively high temperature is required in order to activate the softening or other fabric treating agent on the non-woven sheet and release it into the fabric of the clothing. Most clothes dryers have several heat settings to accommodate different types of clothing. For example, delicate fabrics are preferably dried at lower heat settings and temperatures than clothing made from cotton or the like. At lower heat settings, dry dryer sheets are of marginal effectiveness and therefore delicate fabrics or other clothing dried at lower temperatures may not exhibit the desired softness and feel when worn. This is a pervasive problem in many European countries, as well as other countries around the world, where the high cost of energy makes it a necessity to operate clothes dryers at lower temperatures. On the other hand, it has been observed that clothing dried at high heat settings and temperatures often exhibit an increased amount of static cling and wrinkling. This is true even when the dry dryer sheet is provided with anti-static agents. Furthermore, in addition to creating static cling and wrinkling, high drying temperatures are hard on fabrics, tending to break them down over time.